Thecazellen

ThecaZellen, known in English as theca cells, are specialized stromal cells that form part of the ovarian follicle and surround the granulosa cell layer to create the theca folliculi. They are organized into two major layers: theca interna, a steroidogenic layer, and theca externa, a fibrous, supportive capsule.

Theca interna cells are the primary steroid-producing component of the theca. They respond to luteinizing hormone (LH) and express enzymes such as cholesterol desmolase (CYP11A1) and 17α-hydroxylase (CYP17A1), enabling the conversion of cholesterol to androgens, mainly androstenedione and testosterone. The androgens produced by theca interna cells diffuse to the adjacent granulosa cells, where aromatase converts them into estrogens under the influence of follicle-stimulating hormone (FSH). This cooperative interaction between theca interna and granulosa cells is essential for estrogen biosynthesis during follicular development.

Theca externa consists of fibrous connective tissue and provides structural support to the growing follicle. It contains fibroblasts and smooth muscle-like cells and helps organize the vascular supply that nourishes the follicle.

Origin and clinical relevance: Theca cells originate from ovarian stroma mesenchyme during folliculogenesis. Clinically, tumors of theca cells, referred to as thecoma or theca cell tumors, can secrete estrogen, potentially causing endometrial hyperplasia and abnormal uterine bleeding. Theca cell activity is tightly coordinated with granulosa cell function to regulate follicle maturation and ovulation.